<h4 align="center">
Using Interval Notation
</h4>

<ul>

<li> If an endpoint is included, then use <tt>[</tt> or <tt>]</tt>.
If not, then use <tt>(</tt> or <tt>)</tt>.  For example, the interval
from -3 to 7 that includes 7 but not -3 is expressed <tt>(-3,7]</tt>.


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<li> For infinite intervals, use <tt>Inf</tt>
for <font size="+2">&#8734;</font> (infinity) and/or
<tt>-Inf</tt> for <font size="+2">-&#8734;</font> (-Infinity).  For
example, the infinite interval containing all points greater than or
equal to 6 is expressed <tt>[6,Inf)</tt>.


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<li> If the set includes more than one interval, they are joined using the union
symbol U.  For example, the set consisting of all points in (-3,7] together with all points in [-8,-5) is expressed <code>[-8,-5)U(-3,7]</code>.

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<li> If the answer is the empty set, you can specify that by using
     braces with nothing inside: <code> { } </code>

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<li> You can use <code>R</code> as a shorthand for all real numbers.
  So, it is equivalent to entering <code>(-Inf, Inf)</code>.

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<li> You can use set difference notation.  So, for all real numbers
  except 3, you can use <code>R-{3}</code> or
  <code>(-Inf, 3)U(3,Inf)</code> (they are the same).  Similarly,
  <code>[1,10)-{3,4}</code> is the same as <code>[1,3)U(3,4)U(4,10)</code>.


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<li> WeBWorK will <b>not</b> interpret <tt>[2,4]U[3,5]</tt> as equivalent
 to <tt>[2,5]</tt>, unless a problem tells you otherwise.  
All sets should be expressed in their simplest interval notation form, with no 
overlapping intervals.

</ul>

